The complete data record of a typical industrial-use electronic measuring instrument consists of several segments. These may include calibration parameters for the electronics, for instance for an analog current output value and for the amplification of an electrode voltage measurement as in the case of a magnetoinductive flowmeter. Also included may be calibration parameters for the sensor of the measuring instrument. One such example would be density calibration values for Coriolis-type mass flowmeters. In addition, application-specific parameters may be provided, allowing the measuring instrument to be customized for particular applications. Examples include certain time constants, or the unit of measure by which a process variable is displayed on a monitor. The data record may further include production parameters for instance for the purpose of adapting electronics components to their specific functions in a given measuring instrument, an example being the local bus address of a module. In particular, these parameters are also intended for multi-function component assemblies. And finally, service-specific parameters may be included by means of which the measuring instrument is customized for a given application above and beyond its basic functionality. These parameters are usually protected, meaning that they can be modified only by the manufacturer but not by the user of the measuring instrument.
The complete data record of an electronic measuring instrument may be subdivided into global parameters and local parameters. As a rule, global parameters apply to the measuring instrument as a whole whereas local parameters apply in each case to a limited subsection of the measuring instrument. The local parameters are typically stored on a specifically assigned circuit board and are not usually modified when a measuring instrument is customized for a particular application. In other words, the local parameters are stored where they are needed. In this fashion, when circuit boards or complete modules of the measuring instrument are exchanged, the settings such as calibration values they contain remain permanently intact. For example, the calibration parameters for the current output relate to the analog part of the measuring instrument and therefore have to be exchanged jointly with the latter.
While the electronics-calibration and production parameters are local parameters, the sensor-calibration, application-specific and service-related parameters are global parameters that relate to the measuring instrument as a whole. These global parameters, actively controlling the measuring instrument during its operation, are stored in the main memory of the measuring instrument. That main memory may even be “distributed”, i.e. it may consist of several modular blocks in distributed locations of the measuring instrument. Moreover, backup copies of the global parameters may additionally be saved in one or several other memory areas.
For one example, reference is made to DE 101 48 029 A1 that specifies a primary and a secondary memory from which the parameters can be downloaded into the main memory. DE 101 48 029 A1 also provides for a memory module for standard operating parameters that can be downloaded into the main memory, should both the primary and the secondary memory have failed.
The method described in DE 101 48 029 A1 essentially constitutes a backup process for the operating parameters of the electronic measuring instrument whereby, in the event of at least a partial loss of operating parameters due to the failure of a memory block, the secondary memory backs up the primary memory and vice versa, while in the event of a total loss of the data in the primary and the secondary memories, the default or standard parameters can be downloaded from an additional backup memory module.